Hydraulic device to be connected in a pipe string

ABSTRACT

A vibration-generating device for a pipe string includes a hydraulic cylinder barrel, a hydraulic piston, changeover valves, and a double tubular piston rod. Each of the changeover valves is automatically shiftable. Fluid flows through the piston rod, changeover valves, and cylinder barrel.

BACKGROUND OF THE INVENTION

The present invention relates to a hydraulically operated device adaptedto be connected in a pipe string, specifically coiled tubing. Forexample, the device can be used in order to facilitate pushing of thestring into highly deviated or horizontal wells in connection withworking, and in maintenance operations such as logging, assembling ordisassembling parts, acid and sand washing etc.

It has previously been proposed to provide drill strings withhydraulically operated devices or vibrators to facilitate the advance ofthe string. Thus, U.S. Pat. No. 4,384,625 proposes subjecting the drillstring to vibrations in the form of resonance oscillations to reduce thefriction between the drill string and bore hole wall in deviated wellsto extend the reach in rotary drilling. As an example of a vibrator thepatent refers to a fluid operated eccentric weight, implyingsubstantially transversal vibrations.

U.S. Pat. No. 3,235,014 describes a method and apparatus for generatingaxial vibrations through a drilling swivel to transmit a percussiveeffect to the drill bit. Furthermore, various types of hydraulic hammeror percussion tools are known, which are intended for loosening stickingdrill strings. An example of this type of tool is disclosed in NO patent171 379.

Coiled tubing has substantially lower mass and diameter than drillpipes, which means that a transversally acting resonance vibrator withaccompanying hydraulic motor as proposed in the above U.S. Pat. No.4,384,625 would be rather ineffective when used in connection withcoiled tubing. The main object of the invention, therefore, is toprovide a device that effectively reduces friction, both at the coiledtubing head (lowermost tool section) as well as upwardly along thecoiled tubing itself.

SUMMARY OF THE INVENTION

According to the invention, this object is achieved through a device asdefined in the appendant claim 1. Advantageous embodiments of theinvention are defined in the remaining appendant claims.

A device mounted to a coiled tubing through which pressurized fluid isflowing will continuously perform telescopic (axial) percussions orvibrations propagating along the entire lower part of the coiled tubing,including the coiled tubing head. The vibrations travel backwards alongthe coiled tubing. Due to the steady changes in the direction oftransmission of the vibrations, the effective frictional resistance willbe drastically reduced which will permit the coiled tubing to be pusheda substantial distance into a highly deviated and horizontal well borebefore buckling and getting stuck. Calculations based on an 80° deviatedwell bore indicate an enhanced reach of as much as 3000 m.

The device according to the invention differs from prior vibratorsintended for use in petroleum wells, primarily by the fact that itgenerates a telescopic (axial) vibration at a relatively high amplitude.Existing vibrators as discussed above are primarily designed to provideshort and violent percussive pulses during drilling, or for releasingstuck tools. These hammer tools operate at a much lower vibrationamplitude, implying vibrations of a substantially shorter operationalrange. Thus, they are of little use in enhancing the reach of coiledtubing.

Of course, although the primary object of the invention, as discussedabove, is to provide a vibrator suitable for reducing the pushfrictional resistance of coiled tubing, there is nothing to prevent itfrom being used with advantage also in ordinary rotary drill strings.Furthermore, the purpose of the use of the device need not necessarilybe to reduce friction. Thus, in some cases it may be advantageously usedas a percussion tool, preferably mounted in front of the pipe string.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal cross sectional view of the device ofthe present invention in a first phase of operation.

FIG. 2 is a schematic longitudinal cross sectional view of the device ofthe present invention in a second phase of operation.

FIG. 3 is a schematic longitudinal cross sectional view of the device ofthe present invention in a third phase of operation.

DETAILED DESCRIPTION OF THE INVENTION

The device according to the invention builds on per se well-knowntechnology. Thus, in principle it is in the form of a double actinghydraulic cylinder having automatically operated changeover valves. Asshown in the figures it comprises a hydraulic cylinder 1 including acylinder barrel 4 and piston 6 having a tubular double piston rod 8extending through the barrel end walls 10, 11 respectively. One end ofthe cylinder barrel has a tubular extension 12 receiving and preferablyextending axially somewhat beyond the part of the piston rod 8 thereinwhen the latter is in its outer end position (FIG. 2). The extension 12terminates in a threaded portion 14 formed to mate with a correspondingthreaded portion of a member of a pipe string such as coiled tubing.Similarly, the piston rod end protruding at the opposite end of thecylinder barrel also terminates in a threaded portion 16 adapted to matewith a pipe string member. In the drawings the threaded portion 14, 16are shown as being tapered, but they may just as well be cylindrical, asis now most usual for coiled tubing. In the example shown the cylinderend portion 14 has external threads and the piston rod end portion 16internal threads. However, the arrangement may of course be reversed ifdesirable. The cylinder 1, in its embodiment as shown, is designed to bemounted to the pipe string with its cylinder threaded portion 14 facingforward, i.e., in the direction of advancement of the pipe string.Consequently, in what follows, phrases such as forwards, backwards,foremost, rearmost, front, rear, refer to the direction of advancementof the pipe string (from left to right on the drawing).

The piston 6, which divides the cylinder barrel 4 into front and rearcylinder chambers or annulus 15 and 17 respectively, supports aplurality, in the shown example two, shuttle valves in the form of valvemembers 18 and 20. The valve members 18 and 20 are adapted to be axiallydisplaced between a front port, 22 and 24 respectively, and a rear port,26 and 28 respectively, formed in the piston faces 23, 25, and open intofront annulus 15 and rear annulus 17, respectively. Shifting of theshuttle valves is automatically brought about by mechanical actuationwhenever the piston reaches an end position. The two shuttle valves 18,20 act as an inlet valve and outlet valve respectively, as explained inmore detail below.

A lateral partition 34 divides the interior of the tubular piston rodinto a rear part or inlet passage 36 and a front part or outlet passage38 which, via an inlet opening 40 behind the partition and an outletopening 42 in front of the partition, communicate with the inlet valve18 and outlet valve 20, respectively.

In operation, with cylinder 1 mounted and oriented in a pipe string asdescribed above, the device according to the invention will performsuccessive contraction and expansion phases, activated by fluid, such asdrilling mud, pumped through the pipe string.

In FIG. 1 the device is shown at the start of the contraction phase orstroke. Pressurized fluid flows into and through inlet passage 36, inletopening 40, the open rear inlet port 26 and out into the rear cylinderannulus 17. The fluid pressure in the rear annulus urges the pistonforward relative to the cylinder barrel, while the inlet and outletvalve members 18, 20, urged by the fluid pressure, close the front inletport 22 and rear outlet port 28 respectively, to prevent fluid fromflowing into the front cylinder annulus 15. Fluid in the front annulusflows through the open outlet port 24, through outlet opening 42, intopiston rod outlet passage 38 and thence further to pipe string membersdownstream.

FIG. 2 shows the cylinder at the end of the contraction phase, when thetwo shuttle valves 18, 20 automatically shift as they encounter thefront end wall 11 pushing them backwards to open front inlet port 22 andrear outlet port 28. This causes the pressurized fluid to flow via port22 into front annulus 15 to fill the latter, while the fluid in rearannulus 17 flows out through rear outlet port 28 and opening 42, outletpassage 38 and further through the pipe string. At this point the inletand outlet valve members 18, 20 will be urged by the fluid pressure inthe front annulus to close the rear inlet port and front outlet portrespectively as shown in FIG. 3 to start the expansion phase in whichthe piston, urged by the fluid pressure in the front annulus, movesbackwards relative to the cylinder barrel, until the valve members againshift as they encounter the rear end wall 10 of the cylinder barrel anda new contraction stroke starts as described above.

When the device is to act as a friction reducing vibrator in a coiledtubing, it is normally positioned in between the coiled tubing and toolstring. In order to produce an optimal friction-reducing effect, thevibrations must have a certain amplitude (typical stroke: 10-50 mm) anda frequency high enough (typically 2-5 cycles per second) to permit theinertia of the tool string to force a considerable amount of thevibrations upwards along the coiled tubing. If a long stroke were to bechosen and a correspondingly low frequency, then the device wouldexhibit a functional mechanism different from that described above,since in that case the tool string would reciprocate. During thecontraction phase, the tool string would serve as a frictional anchor,with the device pulling the string after itself.

The vibration frequency is determined by the cylinder volume, stroke andflow rate. On the other hand, with a given cylinder volume and stroke,the flow rate is determined by the fluid pressure and by the effectiveopening areas of the valves 18, 20. Although only two shuttle valves areshown in the schematic drawing, i.e., one inlet valve 18 and one outletvalve 20, in order to minimize the pressure loss across each valve,normally a plurality of valves, e.g., six valves, would be needed (i.e.,three sets alternately distributed as inlet valves 18 and outlet valves20). Furthermore it should be noted that although the piston partition34 is schematically shown as a solid or unbroken inclined wall, ifdesirable it could be adapted to accommodate various valves. Forexample, pressure relief valves and/or flow control valves could beinstalled, closing when the flow rate exceeds a certain level.

As previously mentioned, the above described example of an embodiment ofthe vibrator device according to the invention is schematicallyillustrated in the drawing, since it builds on per se, well-knowntechnical details which a person skilled in the art would be able toimplement in a suitable manner without difficulty. Specifically, inpractice the shuttle valves are conceivable in many forms.

However, in order not to leave any doubt as to the practical feasibilityof the device, the example as shown in the drawing will now be describedin a somewhat more detailed manner. Thus, in the drawing the inlet valve18 is indicated as a cylindrical body slidably supported in inlet ports22, 26 via two pins or shafts 19 (FIG. 3) axially protruding from eitherside of the valve member. In the schematic figures, which primarily aremeant to illustrate the principle of the design and operation of thevibrator according to the invention, these shafts 19 are indicated asfloating in ports 22, 26. In practice they would of course be sized tohave a sliding fit diameter. Further, they would be formed in a mannerto permit fluid to flow freely through an open inlet port. Thus, theshafts 19 could be in the form of perforated pipes, or a perforatedbearing sleeve could be mounted in the ports. The distance between theouter ends of the shafts 19 is slightly larger than the distance betweenthe faces of the piston 6, in order to cause shifting of the valve whenthe outer ends of the shaft encounter end walls 10, 11 of the cylinderbarrel.

The outlet valve 20 is shown as a disk-like body at each end of anintermediate shaft 21 extending through outlet ports 24, 28 and actingas a support for the outlet valve body, in the same manner as describedabove in connection with the inlet valve member. The distance betweenthe outer ends of the disks is substantially equal to that between theend surfaces of the inlet valve shafts, i.e., somewhat larger than thedistance between the piston faces, in order to bring about shifting ofthe valve upon encountering the cylinder end walls 10, 11. The valvemembers 18, 20 could of course be spherical rather than disk-like.Furthermore, for optimal performance, some kind of spring means could beprovided to accelerate the valve shifting and/or to hold the valve moresteady at the end positions. It would not be necessary to explain theseand other details of the valve structure in further details, since aperson skilled in the art would realize what is needed to obtain asatisfactory valve performance.

As for the main dimensions of the cylinder barrel 4, its outer diameterwould normally be equal to or less than the outer diameter of the pipestring to which it is connected, while the length of the cylinder barrelwould depend on the desired stroke of the cylinder 1.

When using the vibrator device according to the invention in connectionwith coiled tubing operations, the device, as noted above, will normallybe connected in between the coiled tubing and the tool string. However,as mentioned, the device according to the invention is also contemplatedas a percussion tool mounted in front of the pipe string, and thenpossibly with a shape different from the front end threaded portion 14.

The cylinder 1 of the example as shown and described is adapted to beconnected to the pipe string with its cylinder end portion 14 facingforward, which means that the fluid would flow in a direction from leftto right in the figures. However, it could just as well be designed fora reversed connection, which means that the fluid would flow from rightto left, since then the two shuttle valves 18, 20 are interchangedrelative to the piston rod partition 34.

What is claimed is:
 1. A vibration-generating device, comprising:ahydraulic cylinder barrel; a hydraulic piston arranged in said hydrauliccylinder barrel so as to form a front chamber and a rear chamber in saidhydraulic cylinder barrel; a plurality of changeover valves within saidhydraulic cylinder barrel, each of said changeover valves beingautomatically shiftable; and a double tubular piston rod, wherein fluidflows through said double tubular piston rod, said changeover valves,said rear chamber, and said front chamber when said vibration-generatingdevice is operational, wherein at least one end of saidvibration-generating device has a threaded portion to be connected to apipe string.
 2. The device of claim 1, wherein a stroke of saidhydraulic piston between a first end wall of said hydraulic cylinderbarrel and a second end wall of said hydraulic cylinder barrel is in arange of 10-50 mm, and wherein a cycle is defined as a reciprocal travelof said hydraulic piston from said first end wall to said second endwall and back to said first end wall, a stroke frequency being in arange of 2-5 cycles per second.
 3. The device of claim 1, furthercomprising a lateral partition arranged within an interior of saiddouble tubular piston rod so as to form a front portion and a rearportion in said interior of said double tubular piston rod, saidchangeover valves comprising a pair of shuttle valves disposed in saidhydraulic piston at opposite sides of said lateral partition, each ofsaid pair of shuttle valves communicating with a respective one of saidfront portion and said rear portion so as to form an inlet passage andan outlet passage for the fluid flowing into and out of said frontchamber and said rear chamber of said hydraulic cylinder barrel.
 4. Thedevice of claim 1, wherein a stroke of said hydraulic piston between afirst end wall of said hydraulic cylinder barrel and a second end wallof said hydraulic cylinder barrel is in a range of 10-50 mm, and whereina cycle is defined as a reciprocal travel of said hydraulic piston fromsaid first end wall to said second end wall and back to said first endwall, a stroke frequency being in a range of 2-5 cycles per second. 5.The device of claim 3, wherein each of said shuttle valves is arrangedwithin said hydraulic cylinder barrel so as to be mechanically shifted.6. The device of claim 5, wherein a stroke of said hydraulic pistonbetween a first end wall of said hydraulic cylinder barrel and a secondend wall of said hydraulic cylinder barrel is in a range of 10-50 mm,and wherein a cycle is defined as a reciprocal travel of said hydraulicpiston from said first end wall to said second end wall and back to saidfirst end wall, a stroke frequency being in a range of 2-5 cycles persecond.
 7. The device of claim 5, wherein each of said shuttle valvescomprises a valve member having a pair a shafts extending in an axialdirection therefrom, said hydraulic piston having a pair of end wallsand having two ports formed in each of said end walls, each of saidports opening into one of said front chamber and said rear chamber, eachof said shuttle valves being axially slidably supported between two ofsaid ports by said shafts so as to shifted when contacting an end wallof said hydraulic cylinder barrel.
 8. The device of claim 7, wherein astroke of said hydraulic piston between a first end wall of saidhydraulic cylinder barrel and a second end wall of said hydrauliccylinder barrel is in a range of 10-50 mm, and wherein a cycle isdefined as a reciprocal travel of said hydraulic piston from said firstend wall to said second end wall and back to said first end wall, astroke frequency being in a range of 2-5 cycles per second.
 9. Avibration-generating device connected to a pipe string, comprising:apipe string; and a vibration-generating device including:a hydrauliccylinder barrel; a hydraulic piston arranged in said hydraulic cylinderbarrel so as to form a front chamber and a rear chamber in saidhydraulic cylinder barrel; a plurality of changeover valves within saidhydraulic cylinder barrel, each of said changeover valves beingautomatically shiftable; and a double tubular piston rod, wherein fluidflows through said double tubular piston rod, said changeover valves,said rear chamber, and said front chamber when said vibration-generatingdevice is operational; wherein at least one end of saidvibration-generating device has a threaded portion connected to saidpipe string.
 10. The device of claim 9, wherein a stroke of saidhydraulic piston between a first end wall of said hydraulic cylinderbarrel and a second end wall of said hydraulic cylinder barrel is in arange of 10-50 mm, and wherein a cycle is defined as a reciprocal travelof said hydraulic piston from said first end wall to said second endwall and back to said first end wall, a stroke frequency being in arange of 2-5 cycles per second.
 11. The device of claim 9, furthercomprising a lateral partition arranged within an interior of saiddouble tubular piston rod so as to form a front portion and a rearportion in said interior of said double tubular piston rod, saidchangeover valves comprising a pair of shuttle valves disposed in saidhydraulic piston at opposite sides of said lateral partition, each ofsaid pair of shuttle valves communicating with a respective one of saidfront portion and said rear portion so as to form an inlet passage andan outlet passage for the fluid flowing into and out of said frontchamber and said rear chamber of said hydraulic cylinder barrel.
 12. Thedevice of claim 11, wherein a stroke of said hydraulic piston between afirst end wall of said hydraulic cylinder barrel and a second end wallof said hydraulic cylinder barrel is in a range of 10-50 mm, and whereina cycle is defined as a reciprocal travel of said hydraulic piston fromsaid first end wall to said second end wall and back to said first endwall, a stroke frequency being in a range of 2-5 cycles per second. 13.The device of claim 11, wherein each of said shuttle valves is arrangedwithin said hydraulic cylinder barrel so as to be mechanically shifted.14. The device of claim 13, wherein a stroke of said hydraulic pistonbetween a first end wall of said hydraulic cylinder barrel and a secondend wall of said hydraulic cylinder barrel is in a range of 10-50 mm,and wherein a cycle is defined as a reciprocal travel of said hydraulicpiston from said first end wall to said second end wall and back to saidfirst end wall, a stroke frequency being in a range of 2-5 cycles persecond.
 15. The device of claim 13, wherein each of said shuttle valvescomprises a valve member having a pair a shafts extending in an axialdirection therefrom, said hydraulic piston having a pair of end wallsand having two ports formed in each of said end walls, each of saidports opening into one of said front chamber and said rear chamber, eachof said shuttle valves being axially slidably supported between two ofsaid ports by said shafts so as to shifted when contacting an end wallof said hydraulic cylinder barrel.
 16. The device of claim 15, wherein astroke of said hydraulic piston between a first end wall of saidhydraulic cylinder barrel and a second end wall of said hydrauliccylinder barrel is in a range of 10-50 mm, and wherein a cycle isdefined as a reciprocal travel of said hydraulic piston from said firstend wall to said second end wall and back to said first end wall, astroke frequency being in a range of 2-5 cycles per second.